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Extracellular ATP is known to inhibit growth of various tumours by activating specific purinergic receptors (P2-receptors). Since the therapy of advanced oesophageal cancer is unsatisfying, new therapeutic approaches are mandatory. Here, we investigated the functional expression and potential antiproliferative effects of P2-purinergic receptors in human oesophageal cancer cells. Prolonged incubation of primary cell cultures of human oesophageal cancers as well as of the squamous oesophageal cancer cell line Kyse-140 with ATP or its stable analogue ATPgS dose-dependently inhibited cell proliferation. This was due to both an induction of apoptosis and cell cycle arrest.

Extracellular nucleotides induce apoptosis and inhibit growth of colorectal cancer cells. To understand the underlying signaling pathways, we investigated the role of nucleotide-sensitive P2 receptors and focused on the receptor-mediated signaling of intracellular Ca2+ and cyclic adenosine monophosphate (cAMP) in two colorectal carcinoma cell lines (HT29, Colo320 DM). Expression and functionality of P2 receptor subtypes evaluated by RT-PCR and [Ca2+]i imaging revealed that solely metabotropic P2 receptors of the subtype P2Y2 were expressed on a functional level in both cell lines. Short-term stimulation of P2Y2 receptors caused Ca2+ mobilization from intracellular stores and a subsequent transmembrane Ca2+ influx. The receptor-induced [Ca2+]i elevation was shown to increase basal-stimulated [cAMP]i moderately and to potentiate forskolin-stimulated [cAMP]i vigorously, since the effects were dose-dependently inhibited by preloading the cells with the [Ca2+]i chelator BAPTA. In contrast, activation of protein kinase C (PKC) did not contribute to a receptor-mediated rise in [cAMP]i, since the PKC inhibitor staurosporine completely failed to reduce P2Y2 receptor-induced increases in [cAMP]i. Prolonged application of P2Y2 receptor agonists induced a time-dependent increase in apoptosis (up to 50% above control values) in both cell lines and caused dose-dependent inhibition of cell proliferation of up to 85% (Colo320 DM) or 64% (HT29). Chelating [Ca2+]i with BAPTA almost completely abolished P2Y2 receptor-induced cell death. Rises in [cAMP]i elicited by either forskolin or cAMP derivatives inhibited growth in both cell lines, too. In line with the potentiating effect of P2Y2 receptors on forskolin-stimulated [cAMP]i increases, costimulation with forskolin and P2Y2 receptor agonists led to synergistic antiproliferative effects. Moreover, a synergistic growth inhibition was observed when coincubating the cells with the P2Y2 receptor agonist ATP and the cytostatic drug 5-fluorouracil, which forms the basis for most currently applied chemotherapeutic regimes in colorectal cancer treatment. Our results demonstrate the growth inhibitory potency of P2Y2 receptors in colorectal carcinoma cells. Receptor-induced [Ca2+]i signaling appears to play a major role in the observed antiproliferative and apoptosis-inducing effects.

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Through the endoscope balloon stricture dilatation is a relatively safe and often effective treatment modality in ileocolonic strictures. The presence of ulcers in the stricture have a worse outcome as do smokers.

The integrin mediated interactions between tumour cells and the surrounding extracellular matrix are thought to play crucial parts in the complex process of invasion and metastasis. It has been previously shown that the expression ofintegrins is differently diminished in a chainspecific manner in human colorectal cancer.

Patients with (previous) head and neck cancer (HNC) are at high risk for developing second squamous cell cancer of the oesophagus. The role of cyclooxygenase-2 (COX-2) in oesophageal squamous carcinogenesis has not yet been investigated in this high-risk group. Therefore, this study examined COX-2 mRNA and protein expression in oesophageal biopsies and resected tissues of 44 HNC patients. The evaluation covered 55 oesophageal tissue samples (18 invasive oesophageal squamous cell cancers, four high-and eight low-grade dysplasias, 25 normal squamous epithelia) from the 44 patients. mRNA levels of COX-2 were measured by real-time PCR using a LightCycler. COX-2 protein expression was studied immunohistochemically and graded by a staining score. COX-2 mRNA was detected in all samples, and its levels correlated positively with the immunohistochemical staining score (Po0.05). COX-2 expression was upregulated during oesophageal squamous carcinogenesis in HNC patients, that is COX-2 expression increased significantly from normal oesophageal squamous epithelium to low-and high-grade dysplasia and finally to invasive squamous cell cancer (Po0.001). Our findings suggest that COX-2 upregulation contributes to oesophageal squamous carcinogenesis in HNC patients. Prospective studies are needed to evaluate the chemopreventive potential of COX-2 inhibitors in this high-risk group.